That’s a DIN speaker socket, https://en.m.wikipedia.org/wiki/DIN_connector
Matching plugs are still readily available
http://www.ebay.co.uk/itm/2-Pin-DIN-Hi-Fi-Speaker-Plug-Cable-Audio-Connector-PACK-of-2-Screw-Connect...
Matching plugs are still readily available
http://www.ebay.co.uk/itm/2-Pin-DIN-Hi-Fi-Speaker-Plug-Cable-Audio-Connector-PACK-of-2-Screw-Connect...